<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var c = 300;
    </script>
    <script>
        //语法错误，只能影响当前块
        var a = 100;
        var b = 200；

        document.write(b);
    </script>
    <script>
        var a = 10;
        document.write(a);
        document.write(c); //可以使用上面代码块的变量
        document.write(b); //解释执行到错误处，后面代码不会执行
        document.write(20);
    </script>
</body>
</html>